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Re: imaginary unit


From: Przemek Klosowski
Subject: Re: imaginary unit
Date: Thu, 27 Apr 2006 13:52:31 -0400 (EDT)

   On 4/26/06, Przemek Klosowski <address@hidden> wrote:
   > Perhaps the use of predefined 'i' should elicit a warning?

   That would be a rather annoying warning. Octave is built with

Agreed, of course; the ideal warning would only happen when you
use 'i' as an imaginary unit---but of course Octave has no way
of knowing your intentions. Perhaps warning should trigger when
'i' (et al) is changed _away_from_ the imaginary unit? That would
only trigger once. 

This actually might be a good idea---behold 'pi' (3.1416); you
can make like Indiana and set 'pi=3' and it'll do it quietly, just
like it would let you define Inf=0, eps=1, e=2, etc.

The famous Euler equation e^(i*pi)+1=0 suddenly starts looking
sinister when you realize that all of 'e', 'i' and 'pi' can change :)

I don't think making the builtin variables readonly is a good idea:
people want to use 'i' as index, and setting 'eps' to different values
might actually be useful to test and tune convergence.

So, what about a warning when changing predefined constants? 

By the way, Mathematica for instance uses I,E, etc, and they are 
readonly: 

In[8]= I*I
Out[8]= -1

In[9]:= I=1
Set::wrsym: Symbol I is Protected.


                     p


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